Hello.  I understand your problem. Since your young , the problems seems to be either related to acidity or some lower chest infection . While in lower chest infection, you should have problem the entire day. Since you are having it on lying down, it makes it nearly clear the probability of acidity problem. Avoid oily and fried food. Don't lie down for 30 minutes after the Meals . Eat small portions of meals multiple times. If you have any acidity or constipation problem , do consult me private for complete treatment protocol